1. Field of the Invention
Example, non-limiting embodiments of the present invention relate in general to an electronic clutch for a power driver, and more particularly to an electronic clutch that may be operational when a tool chuck is actuated (i.e., to open or close the chuck jaws) via power from the power driver's transmission.
2. Description of Related Art
A power driver may have a multi-speed transmission for rotationally driving the tool chuck at various operating speeds. A user may select the operating speed of the power driver via a speed selector.
The power driver may also include an electronic clutch that may interrupt the power supply to the motor of the driver when the torque applied to the motor armature shaft exceeds a trip torque. Here, the current passing through the motor coils may be sensed and used as an indicator of torque performance. Such electronic clutches are conventionally known in this art. For example, a representative electronic clutch is described in U.S. Pat. No. 4,503,370, the entire contents of which are incorporated herein by reference. The electronic clutch described in U.S. Pat. No. 4,503,370 may have a plurality of operating levels. The operating levels may respectively correspond to the operating speeds of the power driver. That is, the trip torque of the electronic clutch may be set depending on the user selected operating speed of the power driver.
The power driver may also include a tool chuck with chuck jaws that may be actuated (i.e., opened and closed) via power from the transmission. Such chuck actuation may be referred to as a power take off (“PTO”) feature. The PTO feature (when closing the chuck jaws) may result in the chuck jaws applying a more than desirable clamping force. Also, the motor of the power driver may be wound to give greater performance (e.g., more torque) when driven in a forward direction than in a reverse direction. This may cause the tool chuck to be tightened to a more than desirable level.
Tool chucks with various PTO features are described in commonly-assigned, Copending Provisional Application entitled “TOOL CHUCK WITH POWER TAKE OFF AND DEAD SPINDLE FEATURES,” filed Apr. 19, 2005, (the “Copending Provisional Application”). The disclosed example embodiments of the Copending Provisional Application are set forth below in sections I-V.